def make_album(singer_name, album_name, number_of_songs=None):
    """创建一个描述音乐专辑的字典"""
    if number_of_songs:
        return {'singer name': singer_name, 'album name': album_name,
                'number of songs': number_of_songs}
    else:
        return {'singer name': singer_name, 'album name': album_name}


print(make_album('Zhou Jielun', 'Jay'))
print(make_album('Wu Bai', 'Falling in love with others is a happy thing'))
print(make_album('Xu Wei', 'Elsewhere', 10))
